1. Field of the Invention
This invention relates generally to computer-based systems and methods for data processing, and more particularly relates to computers and methods utilizing software application programs, particularly spreadsheet application programs.
2. Description of the Prior Art
Generally, spreadsheet application programs are well known in the area of digital computer data processing, such as those disclosed in U.S. Pat. No. 5,416,895 assigned to Borland Inc., U.S. Pat. No. 5,317,686 assigned to Lotus Development Corp., and U.S. Pat. No. 5,359,724 assigned to Arbor Software Corp. These application programs, executed by the processor of a digital computer, typically provide the user with a spreadsheet-like presentation on a cathode ray tube (CRT) display including a grid or chart formed by a series of columns intersecting a series of rows. The intersection of a column and a row forms a cell, into which the user, through the use of computer input and pointing devices, can enter and arrange data. The user may also enter formulas into individual cells that perform operations on the entered data.
Data associated with a cell is called an object and such objects may be in the form of scalar values such as integers, real numbers and strings. Further, objects may be in the form of more complex elements such as video or other graphical images. Nonetheless, the traditional column/row configuration is preferred because such application programs give the spreadsheet user the visual presentation he or she may have become accustomed to from using manual spreadsheets, while at the same time the user is given access to the vast calculating power of the digital computer. Hence, such spreadsheet application programs, being executed on a digital computer, are referred to as electronic spreadsheets.
Still further, certain existing spreadsheets possess the capability of interfacing with a scripting language. The scripting language allows the user to control certain operations and program certain functions into the spreadsheet in an effort to customize the spreadsheet. However, despite the apparent usefulness of these spreadsheet programs, such programs, as well as all other existing spreadsheet programs, suffer from certain inherent limitations. These limitations include, for instance, a lack of flexibility with respect to the types of objects that can be manipulated, a lack of extensibility with respect to customization of spreadsheet operators and functions, and a restriction on the presentation of data associated with each object.
As mentioned, lack of flexibility with respect to the types of objects that can be manipulated is one disadvantage of prior art electronic spreadsheets. For instance, it is frequently desirable to perform an operation involving the comparison of like data elements corresponding to two different sets of data. Many existing electronic spreadsheets have the ability to perform this operation; however, in so doing, each element of each data set must typically be assigned to an individual cell, and depending on the size of the data sets, this approach may consume a multitude of spreadsheet cells. Additionally, the resultant data elements generated from the comparison must be assigned to individual cells, making the entire operation extremely cumbersome and space-consuming. This disadvantage exists regardless of whether the electronic spreadsheet is two dimensional, i.e., capable of displaying one spreadsheet, or multidimensional, i.e., capable of displaying multiple interrelated spreadsheets.
Nonetheless, even in an existing electronic spreadsheet capable of assigning an entire data set to an object in one cell, lack of extensibiltiy with respect to the customization of spreadsheet operators and functions still limits the efficiency of these prior art spreadsheets. Lack of extensibility of existing electronic spreadsheets is best illustrated in view of the rigid operation of the data calculation engines associated with these spreadsheets. A data calculation engine is a software module that performs the cell operations associated with an electronic spreadsheet.
For instance, if a user inputs a first scalar value into a first cell of the spreadsheet, a second scalar value into a second cell of the spreadsheet, and desires a third cell of the spreadsheet to represent the addition of the values in the first and second cell, the data calculation engine will perform the scalar addition operation and provide the electronic spreadsheet with the scalar result. It is possible for the data calculation engine to perform this operation because such an operation is "hard-wired" into the module's repertoire of available cell operations. However, because complex objects such as databases (i.e., large data sets) can occupy a single spreadsheet cell, operations between these complex objects are not possible unless the data calculation engine was originally programmed to understand the nature of the complex object, and further, programmed to perform specific operations thereupon. Therefore, while existing electronic spreadsheets provide users with a scripting language that may allow them to manipulate objects to be placed in cells, the existing spreadsheets do not allow the user to alter basic operations on these objects nor do they allow the creation of new objects.
Still further, existing electronic spreadsheets are restricted in the manner in which data associated with an individual cell can be visually formatted and presented. Referring back to the manipulation of the two data sets, discussed above, traditional spreadsheet programs are limited to presenting each element of each data set in an individual cell, forcing the user to scroll through the columns and rows of the spreadsheet in order to locate one particular element of the data set. Therefore, no method is provided for the user to manipulate the data and view it in a more useful format, such as a chart, a graph or a histogram.
Other computer-based data processing systems have attempted to exploit the functionality of an electronic spreadsheet and at the same time overcome some of these limitations. Such systems include the electronic spreadsheets disclosed by Kurt W. Piersol in "Object Oriented Spreadsheets: The Analytic Spreadsheet Package", OOPSLA 1986 Proceedings (September 1986) and by Marc Levoy in "Spreadsheets for Images", Computer Graphics Proceedings, Annual Conference Series (1994). While the Piersol article discloses an object-oriented electronic spreadsheet, the Piersol spreadsheet possesses a fundamental restriction in that operations in cells are not permitted to alter the value of other cells. The spreadsheet described by Levoy discloses the ability to manipulate complex objects such as graphical images; however, the spreadsheet and its scripting language are geared mainly toward manipulating such graphical objects and therefore do not provide the spreadsheet user with the ability to perform traditional arithmetic operations customary in spreadsheet applications.